Enhancing Mono- and Co-digestion of Poultry Manure by a Novel Post-hydrolysis Ammonia Stripping Approach in a Two-Stage Anaerobic Digestion Process

Abstract

The use of poultry manure (PM) in anaerobic digestion applications at high PM proportions is very limited due to its high nitrogen content since high levels of ammonia in the feedstock can lead to unstable and sub-optimal anaerobic digestion operation. This study investigated three methods to improve methane potential from PM at high PM proportions: (1) co-digestion of PM with a mixed substrate (MS) of a cheese factory and coffee-ground wastes at PM:MS ratios of 100:0, 75:25, 50:50, 25:75, and 0:100; (2) two-stage anaerobic digestion of PM and MS at PM:MS ratios of 100:0, 75:25, and 50:50, and (3) a novel post-hydrolysis ammonia stripping at pH 10 and 55 °C. The results indicated that co-digestion increased the methane potential in the samples due to reduced ammonia levels. A two-stage anaerobic digestion system further improved the methane potential by 21 and 41% in the cases of PM:MS at 100:0 and 75:25, while no improvement was observed in the case of PM:MS at 50:50. Post-hydrolysis ammonia stripping under the tested conditions achieved 79.2, 69, and 78.6% ammonia removal in PM:MS of 100:0, 75:25, and 50:50 and improved methane potential by 200, 150, and 64% when compared with the untreated samples.